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MapReduce >> mail # user >> Map Reduce Question


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Anbarasan Murthy 2012-08-17, 19:00
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Manoj Khangaonkar 2012-08-18, 01:20
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Re: Map Reduce Question
See Hadoop definitive guide and search for chapter on Hadoop features

On Fri, Aug 17, 2012 at 6:20 PM, Manoj Khangaonkar <[EMAIL PROTECTED]>wrote:

> One usage of these is in a secondary sort , which is used , when you
> want the output values from Map sorted (within a key).
>
> You implement a KeyComparator and tell mapreduce to use it to order
> the keys using a composite key.
>
> To ensure that during partioning & Grouping , all the records for a
> key go to the same reducer
> you need to define and set a Partitioner and ValueGroupingComparator.
>
> search for Secondary Sort for more on this topic
>
> regards
>
> MJ
>
> On Fri, Aug 17, 2012 at 12:00 PM, Anbarasan Murthy
> <[EMAIL PROTECTED]> wrote:
> > Hi,
> >
> > I have a question in mapreduce api.
> >
> > Would like to know the significance of the following items under jobconf
> > class.
> > ValueGroupingComparator
> > KeyComparator
> >
> >
> >
> > Thanks,
> > Anbu.
>
>
>
> --
> http://khangaonkar.blogspot.com/
>
NEW: Monitor These Apps!
elasticsearch, apache solr, apache hbase, hadoop, redis, casssandra, amazon cloudwatch, mysql, memcached, apache kafka, apache zookeeper, apache storm, ubuntu, centOS, red hat, debian, puppet labs, java, senseiDB